BESS Degradation capacity and power

Dear  All and Paul, 
I have a question regarding degradation behavior of a Battery (LFP) in a PV-plus-Storage system. In this configuration, the battery cycle is generally constant as the batttery charge from the pv system and discharge at the begining of the night. (Charging from the grid is not allowed in this case). 

I looked on "Data Tables" to check how the capacity and power is degrading but I only see a degradation on total Capacity (MWh). From my understanding, if we have a battery bank of X Power (kW) and Y Capacity (MWh), degradation will have an effect on both factors because of the acumulation of internal resistans on battery cells (X-X*d1 and Y-Y*d2). Does SAM neglect this effect? 
I Attached a summarized table (from data Table) and SAM file.

 






 

Hi Nicolas,

For a description of SAM's battery degradation models, see the listings under "Battery Life" on the Battery Publications page:

sam.nrel.gov/battery-storage/battery-publications.html

You can plot the battery total charge (Ah) and battery voltage (V) to see how those values change as the battery capacity degrades over time. This plot from your file shows the battery power, voltage, current and relative capacity to nameplate over the 25-year life of the project.

 

Best regards,
Paul.

Also, see this issue in SAM's GitHub repository: github.com/NREL/ssc/issues/381 .

Thanks Paul for your reply, 

From the comment on github, I see that the resistance is set as a constant value in Battery SAM model . Is it possible to see the effect on  Maximum Power output with an increase in interal resistance?

From my understanding the limitation on Power will be determinated with (1) C-Rate of the cell and (2) their PCS (power converter system) where are conected. 

Look forward to your reply 
Kind Regards ! 


 

Hi Nicolas,

In SAM's battery model, battery power is not very sensitive to changes in internal resistance.

The cell internal resistance is an input on the Battery Cell and System page under "Battery Voltage," so you could experiment with changing its value there.

Best regards,
Paul.